1. Field of the Invention
The present invention generally relates to a development device, a process cartridge, and an image forming apparatus and more particularly to a development device using what is called the ETH (Electrostatic Transport & Hopping) phenomenon in which two-component magnetic brush development is used so as to charge toner and form an electric field, the toner is transferred to a conveying electric field formed on a conveying base in accordance with force of the electric field, and the toner is transferred to a development area, a development device using what is called a flare phenomenon in which the toner is conveyed in accordance with movement of a surface of a conveying member in addition to the electric field, a process cartridge provided with the development device, and an image forming apparatus.
2. Description of the Related Art
Conventionally, there have been known development devices for performing development supplying developer to a latent image carrier without directly bringing the developer on a developer carrier into contact with the latent image carrier. Patent Document 1, for example, discloses a development device for supplying toner to the latent image carrier by using a conveying member. This conveying member is disposed so as to face the latent image carrier and plural electrodes are arranged on a surface thereof at a predetermined pitch. An alternating voltage of n phases is applied to the electrodes so as to generate a progressive-wave electric field for conveying toner. In accordance with the progressive-wave electric field, the toner is conveyed to a development area facing the latent image carrier while the toner is hopping in the vertical direction. While the toner conveyed to the development area is further hopping in the vertical direction, the toner receive force so as to be directed to the latent image carrier in an image area and to the conveying member in a non-image area, so that the image area is developed.
Patent Document 1: Japanese Laid-Open Patent Application No. 2004-198675
However, in these conventional development devices, unevenness of a toner cloud layer is generated in a supply area, a conveying area, and the development area. Toner moves from the supply area to the development area in accordance with the electric field, so that it is impossible to form a high electric field and supply the toner or to bring a member carrying the toner into contact with the conveying member via the toner. When the member carrying the toner is brought into contact with the conveying member, the toner may be attached to the conveying base in accordance with electrostatic force of the toner, especially, image force and non-electrostatic force (Van der Waals force, in particular). This is referred to as “adhesion”. When the toner is supplied in a non-contact manner so as to reduce the adhesion, a status of toner supply becomes uneven because of a supply gap and an uneven status of a magnetic brush. Further, the conveying member is formed using glass or resin with relatively high resistance and has at least a base layer, an electrode layer, and a surface layer. Thus, unevenness upon manufacturing such as resistance distribution, surface roughness distribution, and surface wettability may have an influence on an electric field to be formed. Moreover, in the development area, charge amount distribution becomes broad in addition to the supply and conveying, so that electric potential of the toner cloud layer becomes uneven depending on position. This has an influence on developing bias and an effective developing bias is fluctuated and becomes unstable.